1. Field of Invention
The present invention relates to a technical field of an active-matrix-type electro-optical device, and more particular, technical fields of an electro-optical device having a structure where a thin film transistor (Thin Film Transistor; hereinafter referred to as “TFT”) for switching a pixel is included in a laminated structure on a substrate, a method for manufacturing the same, and an electronic apparatus having the same as a light valve. The present invention also relates to a technical field of an electrophoresis device, such as an electronic paper, an EL (electroluminescent) device, and a device using an electron emission element (a field emission display and a surface-conduction electron-emitter display).
2. Description of Related Art
In an active-matrix-type electro-optical device, when incident light is exposed to a channel region of a pixel switching TFT provided in each pixel, excitation due to light causes light-leakage current so that properties of the TFT are changed. Particularly, in an electro-optical device for a light valve of a projector, because the intensity of incident light is very high, it is important to shield a channel region or peripheral region of the TFT from incident light.
Therefore, in the related art, such channel regions or peripheral regions are formed of light-shielding films defining opening of each pixel provided at a counter substrate, or data lines which are made of metal film such as Al (aluminum) or the like and pass over TFTs on a TFT array substrate. Further, light-shielding films made of high-melting-point metal or the like may be sometimes provided also under the TFTs above the TFT array substrate.
As described above, when light-shielding films are provided below the TFT, back side reflected light from a TFT array substrate or returning light, such as transmitted light transmitting through a prism from another electro-optical device, when a plurality of electro-optical device and prisms constitute one optical system, can be in advance prevented from being incident on the TFT of the electro-optical device.
However, there are the following problems with regard to each light-shielding technique described above. That is, first, according to a technique that a light-shielding film is formed on a counter substrate or a TFT array substrate, because the light-shielding film is separated through, for example, a liquid crystal layer, an electrode, an interlayer insulating film or the like far apart from the channel region in three dimensions, it is not sufficiently shielded from light incident between them at an angle. Particularly, in a small-sized electro-optical device used as a light valve of a projector, because incident light is a light beam obtained by wringing light from a light source through a lens, and includes unnegligible slant-incident component, for example, 10% slant-incident components at ten to fifteen angles from a vertical direction with respect to a substrate, being insufficiently shielded from such slant-incident light may be practically problematic.
In addition, light, which travels from a region free of light-shielding film to an electro-optical device, reflects onto a top surface of a substrate, top surfaces of light-shielding films formed on the substrate, or bottom surfaces of data lines, that is, inside surfaces of sides adjacent to channel regions. Sometimes, multi-reflected light, which is obtained by reflecting such reflected light onto a top surface of the substrate or inside surfaces of the light-shielding films or data lines again, may finally arrive onto channel regions of a TFT.
Particularly, as high precision of electro-optical device or fine pixel pitch is facilitated to meet recent, general requirements of high-quality display image, or light intensity of incident light is increased to display brighter image, it is more difficult to execute sufficient light shielding using various light-shielding techniques described above. Quality of display image may bercome worse due to flicker generated by characteristic change of the TFT transistor.
Further, although formation regions of light-shielding film may be broadened so as to enhance such light-resistant property, because enhanced aperture ratio of each pixel is basically requested to enhance brightness of display image, it is difficult to accomplish such enhancement of light-resistant property by broadening formation regions of the light-shielding films. Also, as described above, considering inside-reflected light or multi-reflected light due to light-shielding films, that is, lower light-shielding films under the TFT or upper light-shielding films above the TFT made of data lines and the like, optionally broadening the formation regions of light-shielding films will result in increase of such inside-reflected light or multi-reflected light, which is a difficult problem to be addressed.